Typically, a conveyor belt is supported by rollers or a slider bed. The sides of the belt are normally angled upwardly to form a trough in the belt. Usually the trough is either 20, 35, or 45 degrees.
In a slider bed the belt slides on steel or some type of low friction plastic. As the width, load and speed of the belt increases the friction increases to a point that the heat build-up between the belt and the slider bed causes destruction of both the belt and the slider bed.
In high impact loading situations, the conveyor belt may be damaged when a slider bed is used. When sharp material falls on the belt supported by the slider bed, the slider bed does not absorb or dissipate the energy sufficiently, so the conveyor belt may be cut or gouged. In certain situations, a cushioning layer is disposed beneath the slider bars to dissipate the impact forces. However, the cushioning layer may not sufficiently dissipate the impact energy for large sharp materials, leading to belt damage.
In a belt supported by rollers the friction is substantially eliminated. However, the belt tends to sag between successive rollers due to the weight of the material and the belt. This sagging causes several problems. For instance, the metal skirt in the area where material is loaded onto the belt tends to become scalloped causing converging pinch points to develop between the belt and the bottom edge of the skirtboard. These pinch points cause material entrapment and resultant damage to the belt.
Further, a resilient seal is typically provided on the outside of the skirtboard. The seal is adjusted to operate in contact with the surface of the belt to seal the fine particles of material and dust from spilling. The sagging of the belt and material between the rollers causes loss of contact between the seal and the belt thus allowing spillage of material from the belt.